The three-week battle to keep a brain-dead Oakland girl on a ventilator could complicate efforts to determine Jahi McMath's precise cause of death, some experts say.

The Alameda County Coroner issued a death certificate for the 13-year-old girl Friday, 23 days after Jahi was declared brain dead, but said the document is incomplete because no cause of death has been determined pending an autopsy, which has yet to take place.

"It does make it more difficult," Alameda County Sheriff's Sgt. J.D. Nelson told NBC Bay Area when asked if delaying an autopsy could affect figuring out how someone died. "It can change a lot of things when the bodily functions continue. In fact, we may not be able to determine a cause of death."

Nelson, who serves as spokesman for the medical examiner's office, shares this sentiment with a prominent bioethicist, who says the delayed autopsy could also affect any future legal proceedings in the case.

"When you don't get an exam relatively quickly, it puts everything into dispute," said Arthur Caplan, head of the Division of Bioethics at New York University Langone Medical Center in New York City and a regular NBC News contributor. "The evidence into what caused the bleeding will be harder to determine, and the ability to show what happened - and the liability - will become way more difficult. The more time you delay, the more difficult it is to establish cause of death because you've lost control of some of the evidence."

It remains to be seen whether any of this evidence will make its way into a lawsuit and affect the outcome of one if a suit is ever filed.

Jahi's family attorney, Chris Dolan, a well-known Bay Area malpractice attorney, has not sued Children's Hospital and told NBC Bay Area on Monday he "didn't plan to sue." But he stopped short of saying that he would not sue sometime down the road.

Late Sunday, Jahi was moved from Children's Hospital to an undisclosed "Catholic facility" that offered to take her after doctors at the Oakland hospital said there was nothing they could do for Jahi, who died on Dec. 12 following complications with a Dec. 9 surgery to cure her sleep apnea. She suffered unknown complications after a series of three simultaneous tissue and tonsil removal surgeries, which caused bleeding and a heart attack.

Because her heart is beating, her family insists that she is alive. Dolan, however, on Monday said Jahi was in "bad shape" after her stay at Children's Hospital and was being given potassium, antibiotics and other nutrients at her new facility.

P. Michael Murphy, past president of the International Association of Coroners and Medical Examiners Association and the current Coroner of Clark County in Las Vegas, acknowledged that there can be subtle to pronounced changes that occur to a body after brain death. He has no personal knowledge of Jahi's case, but has been following it closely in the media.

But he added that forensic pathologists are typically "very good at deciphering" how people died in various "degrees and conditions." Murphy also added that, in most cases, hospitals keep meticulous details of a patient's records, which often aid medical examiners on what led up to death.

"The quicker the exam, the better, certainly," Murphy said by phone on Monday. "But they are trained to report on what they find."

Robert "Rocky" Shaw, San Bernandino County Coroner and president of the California State Coroners Association, agreed with Murphy in that in this case, the hospital's medical records would be ample in determining a cause of death; a body would not have to be opened up.

Some of what has already happened in Jahi's body has been documented in federal court filings written by Children's Hospital doctor Heidi Flori, a pediatric critical care physician who has overseen some of Jahi's care. These filings would have been argued in court on Tuesday, as Children's Hospital did not wants hospital doctors to perform a tracheostomy or put a gastrointestinal tube into Jahi before moving her out of the hospital. That argument is now moot, because Jahi has left the hospital.

"While allowing post-morten bodies to be supported for over three weeks after declaration of death appears to be unprecedented, it is the medical team's complete conviction that nothing can be done to stop the natural progression of Ms. McMath's post-mortem bodily deterioration which is already underway," Flori wrote.

Flori stated that Jahi has lost all brain function, from emotions and sight, to the ability to maintain heart rate, temperature and breathing. She stated that Jahi is not like Terri Schiavo or Israeli Prime Minister Ariel Sharon, who were or are in vegetative states, because Jahi did not simply sustain a brain injury.

Since her declared death, Jahi has not had a real bowel movement in weeks, Flori wrote, she can not regulate her body temperature, her blood pressure has dropped tremendously, and her bodily secretions are becoming "malodorous."

In fact, Flori wrote that any medical intervention to try to "help" Jahi may actually be detrimental.

"They simply will not bring her back to life nor enable others to do so," Flori wrote. "Indeed, such measures may be well counterproductive, perhaps even resulting in expedited cardiopulmonary cessation."